Sockets having a set screw therethrough to lock a post or tube against rotation or slippage, are well known in the art. Particularly, anchor sockets, such as those for swimming pool ladders are known as, for example, the socket disclosed in U.S. Pat. No. 1,611,935. Generally, such sockets are made totally of metal so that the set screw does not strip the hole with repeated usage. Metal, however, is increasingly expensive, particularly rustproof or non-corrosive metals; other metals undesirably corrode. In addition, metal is expensive to fabricate. It has been suggested that such sockets be made of ceramic material or of plastic which are inexpensive, easy to fabricate by molding and non-corrodable, but in such cases the set screw strips the threads after repeated use.